Ceramic bonded grinding wheels and tools such as honing sticks (also referred to as glass bonded or vitreous bonded, or vitrified), have been made by pressing wetted mixtures of bond and abrasive in a closed mold to form a "green" (unfired) shape which is sufficiently strong to maintain its shape, while supported on the bottom only, during the firing operation which softens (matures) the glass so that upon cooling to room temperature, a strongly bonded wheel is produced. Sometimes, particularly when expensive "superabrasive" grits (diamond or cubic boron nitride) are employed in an annular grinding section (rim type wheels), the grinding section is still formed by pressing in a closed mold, but is attached to a ceramic center or core.
Making vitrified wheels or hones by the casting of a mix into open molds, without pressure, is an older method, which has been replaced by the cold pressing technique in closed molds.
One difficulty with the cold pressing method, particularly when wide rim wheels are made, is lack of uniform density across the axial width of the rim, due to the fact that with conventional equipment the pressure must be applied uniaxially. Another difficulty is the expense of molds and the difficulty of filling the molds.
The present invention provides a method for making rim-type ceramic bonded wheels without the use of molds. It is particularly suited to the manufacture of superabrasive wheels and to wide wheels.